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California company cooking up concrete solutions to cement’s carbon problem

On the edge of a nondescript industrial park in Lancaster, at the site of an abandoned driving range, glimpses of a 55-foot tower outfitted with black pipes and cameras, and which sometimes glows with the light of many suns, suggest something out of the ordinary is happening behind the property’s gates.

Here, Pasadena-based startup Heliogen is perfecting its version of a concentrated solar power plant. A field of mirrors have been programmed to follow the sun and beam light up to a tower-top receiver, which is linked to a system that can capture and store intense heat.

The goal, chief scientist Steve Schell explains, is to help all sorts of energy-intensive industries use the sun rather than fossil fuels to keep their operations running 24 hours a day without adding carbon to Earth’s atmosphere. And the company just won a $4.1 million grant from the Department of Energy to pilot a system that could help decarbonize one massive and particularly challenging industry: cement.

While it doesn’t often get the same attention as sectors like oil and gas, the cement industry is responsible for an estimated 7% of all global carbon emissions, producing some 2.7 billion tons of carbon dioxide per year. Put another way, if cement producers were a country, they’d be the No. 3 carbon emitter in the world behind China and the United States.

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The busiest and therefore heaviest carbon-producing cement plant in California is in San Bernardino County. Cemex’s plant on the northern edge of Victorville was responsible for more than a quarter of carbon emissions produced by the sector in 2019, or nearly as much carbon as all railroad operations statewide.

Three of California’s seven active cement plants are in San Bernardino County’s high desert, which is rich with the material’s key ingredient of limestone. Combined, the Cemex plant, a CalPortland Company facility in Oro Grande and a Mitsubishi Cement plant in Lucerne Valley emit nearly as much carbon from their three sites as California’s entire aviation sector.

California’s cement plants have made significant strides in reducing their carbon footprint over the past two decades largely by making their operations more energy efficient. Data from the state Air Resources Board shows that the improvements helped drive cement-related `emissions down 17% from 2000 to 2018.

Still, the industry has a long way to go to hit targets set by Senate Bill 596, which says cement companies in California must produce 40% less carbon by the end of 2035 and hit net zero by the close of 2045. That’s where innovations — like the one Heliogen is testing in Lancaster, and others in the works around the globe — could come into play.

Changes to state regulations, financial incentives and buy-in from customers also will be needed if the industry is going to hit state targets, according to Tom Tietz, executive director of the California Nevada Cement Association. And regulators will have to grapple with some thorny issues, such as the role of carbon capture and other controversial options.

By July 1, the California Air Resources Board is required to publish its plan for getting the cement industry to that 2045 goal. The agency is working with the industry and innovators on that plan now, with input accepted through Nov. 30.

If California can crack the code on carbon-free cement, Tietz and others hope the state can quite literally pave the way for a cleaner global industry — and a cooler planet.

Just use less?

Global emissions from cement production are increasing year over year, even as the process itself gets cleaner in most places. That’s because cement is the primary ingredient used to make concrete, which is the second most commonly used material in the world behind water.

The simplest way to cut emissions from an industry is to either use less of the product it makes or to switch the product out for a cleaner replacement. But while we can reduce emissions from, say, agriculture by eating less meat, we can’t build fewer homes and roads and other infrastructure as the population grows. And while we can slash transportation emissions by switching to electric vehicles, there’s no substitute on the market that can compete with cement’s performance, availability and price point.

There’s still room to use less cement without halting development or replacing the trusted material entirely, argues Paul Adeleke, spokesman for the Global Cement and Concrete Association, which set its own carbon-free goal of 2050.

There’s solid data to show that many infrastructure projects could use less cement than what’s now required in local building codes. And there’s potential to repeatedly recycle concrete, which Adeleke said is already a common practice in other countries.

“We have to agree that, to some degree, demand for concrete cannot continue to accelerate in the way that it has over the course of the last decades.”

But eliminating carbon from the industry entirely is a heavy lift considering carbon emissions are currently a baked-in byproduct of making industry standard portland cement in two ways.

Replace fossil fuels

To produce traditional cement, manufacturers grind up limestone, combine it with other minerals, and preheat them in a large tower to 900 degrees Celsius. Next, the materials go into a massive rotary kiln, where they can reach up to 1,550 degrees. The process, known as calcination, alters limestone’s chemistry and produces solid gray clumps called clinker. Clinker is combined with gypsum and pulverized again to form the familiar cement powder that, when combined with water and aggregates, such as sand, makes concrete.

It takes lots of fuel to get towers and rotary kilns to such high temperatures. And, for now, most cement plants rely on fossil fuels such as coal, natural gas or oil to reach those temperatures, with 60% used in the preheating stage and the other 40% used in the kilns. Burning that fuel creates a third of the carbon emitted by the cement industry, and trading out oil or coal for alternative fuels could eliminate hundreds of millions of tons of carbon each year.

Heliogen’s initial plan is to replace all fossil fuels now used in the preheating stage of cement calcination, Schell said. They aim to build a system with a vacuum that will suck powderized limestone and other minerals to the top of its tower. There, the materials will be hit with concentrated solar power, which will start the chemical reaction.

Because rotary kilns need to get so consistently hot for the second phase of calcination, Schell said they believe the best option is to send the preheated materials there next, but to replace the fossil fuels used in that stage with a clean source such as hydrogen — which, conveniently, also can be created using concentrated solar power.

Heliogen is still finalizing its contract for the $4.1 million grant project with the Department of Energy. Schell hopes they’ll be able to build a demonstration project for solar-powered cement calcination in 2025, a pilot project by 2028 and have the process operating commercially in time to help the state’s cement plants hit the 2035 goal to reduce emissions by 40%.

Other countries are experimenting with heating cement plant kilns by burning waste, from plastics to food scraps. But Tietz said that option is limited under current California laws.

But even if cement plants could be converted entirely to renewable fuel sources, their carbon emissions would be reduced by only a third. The chemical reaction triggered by calcination, when limestone is converted to clinker, produces the other two-thirds of the carbon dioxide emitted by the cement industry. And that part of the equation is even trickier to solve.

Mix it up

To slash carbon emissions from the non-fuel side of cement production, innovators need to alter the calcination process or swap out the materials use. Either option must work without compromising the performance or significantly upping the price of end products such as concrete.

One such tweak is already commercially viable, though Tietz said it’s not yet widely used in California.

In January, Caltrans approved the use a new product called portland-limestone cement, or PLC, in all of its road projects. PLC contains a bit less clinker, with raw, pulverized limestone mixed in as a replacement during the final grinding stage. That small change cuts cement-related carbon emissions by 10%.

With Caltrans reporting it used 325,000 tons of cement for work on state highways in 2017 alone, switching to PLC could reduce emissions by 28,000 tons each year. That equates to taking more than 6,000 gas-powered cars off the road.

CalPortland announced this spring that it had converted its cement plant in Mojave to producing all PLC. Plants can use the same materials and equipment, Tietz said. And since it takes less energy to make a product with less clinker, he said costs for PLC are the same as traditional cement.

Some countries have mandated use of PLC, while others offer incentives to make the switch. But Tietz said more plants would likely change to PLC now if architects and engineers started designing projects that call for it.

To shore up demand for green cement, former Secretary of State John Kerry, now the U.S. Special Presidential Envoy for Climate, announced during the United Nations’ COP27 climate conference in Egypt earlier this month that companies, including General Motors, have committed to buying at least 10% “near zero” concrete by 2030. Kerry said the move “will drive critical investment in next-generation technologies.”

That could include San Diego native Tim Sperry’s startup, Carbon Limit, which makes an additive that he says can replace nearly a third of the cement that’s used to form concrete. He said it creates a product that’s a bit harder and more durable while cutting the carbon footprint by 27%.

Sperry’s product also is designed to attract carbon dioxide in the air and store it in the finished concrete. That’s helped Carbon Limit win a U.S. Army grant and to attract attention from cement companies around the world.

There are many regulatory and logistical hurdles to get such products to market, Sperry acknowledged. But he said interest is high — particularly in California, where he said companies are willing to consider big moves in the face of coming mandates.

Capture it

If cement plants eliminate all fossil fuels and pivot to alternatives that require less clinker, that could cut their carbon emissions in half. But every industry professional said they see only one viable option for keeping the other half of the industry’s carbon from entering the atmosphere.

“Carbon capture is an absolutely essential component of meeting the law and our goals,” Tietz said.

With carbon capture and storage, cement plants would install systems to capture the carbon dioxide generated during calcination. That carbon would be compressed and transported via pipeline, truck or rail. Then it would get injected into underground rock formations for permanent storage. (Companies are trying to make a wide variety of products, such as plastics, from recycled carbon, though most are still in the demonstration phase.)

Carbon capture technology hasn’t been used to scale at a cement plant, with Tietz noting high capital costs, permitting barriers and risks around the untested process. The first such system is expected to come online in Norway in 2024.

Cemex has been working for two years on a pilot carbon capture and storage system at its Victorville plant. The project — a partnership with Carbon Clean, RTI international and Oak Ridge National Laboratory — has partial funding from the Department of Energy.

“As the state’s largest cement plant, CEMEX’s Victorville plant is an important site for research,” said Jerae Carlson, a spokesperson for Cemex. “We are learning by doing, putting our plans into action.”

Environmental groups remain heavily critical of carbon capture programs, citing risks around transportation and storage. Projects in other industries also have so far underperformed, and they worry that letting industries capture emissions gives them a green light to just generate more.

“Pinning the hopes of decarbonizing the cement industry on carbon capture and storage is a pipe dream,” said Victoria Bogdan Tejeda, a staff attorney at the Center for Biological Diversity.

“This technology not only overpromises on greenhouse gas reduction, it’s extremely dangerous and expensive. Instead, regulators and the industry should focus on using proven approaches such as alternative raw materials, renewable electricity and increased efficiency to reduce emissions.”

California company cooking up concrete solutions to cement’s carbon problem

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